WASHINGTON — As housing prices soared last year, an eye-popping 43 percent of first-time home buyers nationwide purchased their homes with no-money-down loans, according to a study released yesterday by the National Association of Realtors.

The trend is potentially ominous. The real estate market is cooling in some areas, and rates on adjustable-rate loans are creeping up. As a result, some no-money-down buyers could owe more than their homes are worth.

The proportion of no-down-payment buyers is smaller in Hawai'i. John Gray, executive vice president at Bank of Hawaii, one of the state's largest mortgage lenders, estimated that 5 percent to 10 percent of first-time buyers in Hawai'i used a zero-down mortgage.

The reasons: Compared to the Mainland buyer, local first-time buyers tend to be more conservative and are more likely to turn to relatives and savings to help with their first purchase, he said.

What's more, a local seller is more likely to accept an offer with a substantial down payment since that buyer has a better chance of completing the purchase than a buyer who is putting no money down, he said.

Nationwide, the median first-time home buyer scraped together a down payment of only 2 percent on a $150,000 home in 2005, the NAR found.

Already, home prices in many areas are declining, and the "For Sale" signs are posted longer. There's now at least a 50 percent risk that prices will decline within two years in 11 major metro areas, including San Diego, Boston, Long Island, N.Y., Los Angeles and San Francisco, according to PMI Mortgage Insurance's latest U.S. Market Risk Index.

"In a number of areas, particularly on the coasts, they have a high risk of price declines in the next two years," says Mark Milner, chief risk officer of PMI.

Red-hot home building, acquisitions, remodeling and refinancing in recent years helped drive the economy and raise fears of a real estate bubble. Dean Baker of the Center for Economic and Policy Research says that if housing prices fall at least 10 percent, it could be even more damaging than the collapse of the high-tech stock bubble in 2000.

"If we do get a spike in mortgage rates, and a modest decline (in the housing market) turns into a rout, there's almost no bottom to that," Baker says. "That's a crash scenario."

Baker and other economists are concerned that many lenders have pushed a series of creative but potentially dangerous loans to help more Americans afford a home. The traditional 30-year loan with a fixed rate remains the most popular way of financing, according to the Mortgage Bankers Association. But about one-third of homeowners take out riskier loans, such as interest-only or flat-minimum-payment mortgages.

"These nontraditional loans transfer risk to the borrower," Milner says.

NAR President Thomas Stevens says he isn't worried that nearly half of first-time home buyers put no money down, but adds, "If the number was higher than that, I'd be concerned."